The present disclosure relates to suspension systems for vehicle seats, particularly suited for tractors and other off-road equipment.
Certain vehicles, and particularly off-road equipment, often utilize seat suspensions to provide a comfortable ride for the operators of such vehicles. In an effort to reduce the stress and fatigue on the operator and to provide comfort to the operator of such vehicles, suspension systems are employed to reduce vibration and limit vertical acceleration experienced by the operators. These suspension systems must be configured to account for many factors such as the wide range of vibration and movements induced by different terrains, varying operator masses and even the seating position and orientation of the operator. A suspension system that can reduce vibration and vibration acceleration over various terrains for a range of operators is very desirable, particularly where the operator must be seated within the vehicle for long periods of time.
Many of these vehicles have relatively small cabins for housing the operator and operator controls. As such, the seats are often straddle mounted over the transmission of the vehicle. This straddle-mount position limits the space or envelop available for the more typical suspension system located under the seat. Consequently, the suspension system is often rear mounted, that is located behind the seat. A typical behind-the-seat suspension system uses springs attached to the operator seat to soften rebounds and absorb vibration caused by the terrain.
Traditionally, behind-the-seat suspension systems affix one end of one or more springs to a frame and the other end directly to the seat back. The placement of the springs in this manner typically creates a 1:1 ratio between the compression/extension of the spring and the vertical translation of the operator's seat. That is, if the seat moves down an inch, the springs also extend downwardly approximately an inch. Many of these systems also employ a dampening device or shock absorber that also has an approximate 1:1 ratio with the movement of the seat. Seats with a 1:1 ratio between the seat and suspension spring movements tend to have ride performance characteristics that underperform, particularly in certain governmental certification testing programs. Additionally, the springs in such systems tend to undergo significant wear thereby requiring frequent repair and replacement of the suspension components. These problems with prior rear mounted suspension systems are further aggravated as the mass of the vehicle operator increases.
There is a need therefore, for a rear mounted or behind-the-seat suspension system that can accommodate a range of operator masses and that can reduce vibration and vibration acceleration for a wide range of terrains.